CAIE IGCSE Chemistry Electrolysis Question Bank

Practise predicting electrode products in molten and aqueous electrolytes, writing balanced half-equations and explaining electroplating observations.

Exam points

identify ions present and predict which product forms at each electrode under stated conditions
write balanced reduction and oxidation half-equations with electrons on the correct side
explain electroplating changes through metal deposition at the cathode and anode dissolution

Covered syllabus points

4.1.1—Electrolysis as the decomposition of 4.1.2—In simple electrolytic cells: (a) the 4.1.8—Transfer of charge during electrolysis 4.1.3—Products and observations during 4.1.4—Metals or hydrogen are formed at the 4.1.5—Predict the identity of the products 4.1.6—Metal objects are electroplated to 4.1.7—Metals are electroplated 4.1.9—Products formed at the electrodes and 4.1.10—Predict the identity of the products 4.1.11—Construct ionic half-equations for

[Maximum number: 6]

This question is about chemical reactions and electricity.

(a)

The diagram shows the apparatus used in the production of electrical energy in a simple cell.

Figure for Question (a) — CAIE IGCSE Chemistry

The zinc electrode dissolves in the electrolyte forming $\mathrm{Zn}^{2+}(\mathrm{aq})$ ions.

[ 1 ]

(i)

Draw an arrow on the diagram to show the direction of electron flow.

[ 1 ]

(b)

Electricity can be used to break down aqueous or molten ionic compounds.

[ 1 ]

(i)

Name the process which uses electricity to break down aqueous or molten ionic compounds.

[ 1 ]

(c)

Brine is concentrated aqueous sodium chloride.

[ 4 ]

(i)

Name three substances which are manufactured by passing electricity through brine.

1
2

3

[ 3 ]

(ii)

Name a different substance formed when molten sodium chloride is used instead of concentrated aqueous sodium chloride.

[ 1 ]

[Maximum number: 12]

This question is about electricity and chemical reactions.

(a)

Aqueous copper(II) sulfate is an electrolyte.

The electrolysis of aqueous copper(II) sulfate using inert electrodes forms:
- copper at the cathode
- oxygen at the anode.

[ 6 ]

(i)

State what is meant by the term electrolyte.

[ 2 ]

(ii)

State what happens to the colour of the aqueous copper(II) sulfate as this electrolysis progresses.

[ 1 ]

(iii)

Write an ionic half-equation for the formation of copper at the cathode.

[ 2 ]

$\mathrm{Cu}^{2+}+2 \mathrm{e} \rightarrow \mathrm{Cu}$

M1 $\mathrm{Cu}^{2+}$ and (any number of) e on left hand side

M2 equation correct

(iv)

Give the formula of the ion that forms oxygen at the anode.

[ 1 ]

$\mathrm{OH}^{-}$

(b)

The electrolysis of aqueous copper(II) sulfate is repeated using copper electrodes.

State what happens to the anode.

[ 1 ]

(c)

Spoons can be electroplated with silver.

[ 5 ]

(i)

Name the substances used as:
the anode (positive electrode)
the cathode (negative electrode)
the electrolyte.

[ 3 ]

(ii)

State two reasons why spoons are electroplated.

1

2

[ 2 ]

[Maximum number: 2]

Aluminium is extracted from aluminium oxide by electrolysis.

Aluminium can be extracted by electrolysis using the apparatus shown.

Figure for Question 4.1 Electrolysis question 3 — CAIE IGCSE Chemistry

Name the type of particle responsible for the transfer of charge in
the wires, the electrolyte.

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Covered syllabus points

4.1 Electrolysis question 1

Question (a)

Question (i)

Question (b)

Question (i)

Question (c)

Question (i)

Question (ii)

4.1 Electrolysis question 2

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (b)

Question (c)

Question (i)

Question (ii)

4.1 Electrolysis question 3